Traveling vehicle systems have been used for transporting articles, using traveling vehicles including overhead traveling vehicles.
A semiconductor factory producing semiconductor devices is, for example, separated into areas called “bays”. One bay is assigned for each production process. Each bay has a closed path on which overhead traveling vehicles travel in one direction.
On each closed path, each of the traveling vehicles transports semiconductor wafers between manufacturing machines in the bay.
Furthermore, the closed paths of the bays are connected with each other via a connecting path. A product undergoes one process in a bay. Then the product is picked up by an overhead traveling vehicle in the bay, and transported to another bay in the succeeding process through the connecting path.
Including the closed paths, the connecting path connecting the closed paths with each other, and overhead traveling vehicles, a traveling vehicle system has to efficiently transport articles.
Hence there are techniques disclosing how to efficiently move the traveling vehicles in the traveling vehicle system.
For example, a technique in Patent Literature 1 introduces a controller for controlling overhead traveling vehicles. The controller keeps tracking on the congestion state of the traveling path, and informs each of the overhead traveling vehicles of the state. Hence each overhead traveling vehicle can determine a traveling route depending on the congestion state.